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Friday, June 28, 2013

The Board of Longitude: What does spaceflight have to do with a watchmaker, James Bond, and a deadly shipwreck?

by J.A. Beard

In 2004, space travel enthusiasts cheered the awarding of the Ansari X Prize for sub-orbital flight. For those unfamiliar, the prize was awarded for a demonstration by a private entity of launching a reusable manned spacecraft into near-outer space twice within two weeks (100 kilometers). The prize itself was worth ten million dollars, but the winners of the prize, and for that matter most of the people attempting to earn the prize ended up putting considerably more money into earning the prize for various reasons (seeking glory, seeking the attention winning the product would grant for business ventures).

The X Prize Foundation itself, which has several prizes dedicated toward impressive achievements, is simply interested in stirring innovation in particular areas that might aid humanity in general.

This is of course not a new idea. Even the Ansari X Prize itself had the goal of helping promote efforts in space by entities other than government agencies. The idea being that such efforts would lead to an expansion of private efforts into the last frontier, something that is needed given the stagnation of government programs.

That particular prize was inspired by certain aviation prizes in the 20th century, but the idea of offering a prize to encourage people to develop technologies that would aid in travel also made an appearance in Georgian England, though in this case, it was driven by a government prize.

Now, of course, back in Georgian England, space travel and even aerial travel weren’t particularly areas that people were worried about trying to crack. They had a more fundamental problem they were attempting to solve for sea-going vessels: knowing your longitude.

Of course, today, we have satellite GPS systems to deliver latitude and longitude with extreme precision. In the 18th century, even with centuries of maritime tradition, navigation was a far trickier affair.

Latitude, at that point, wasn’t a major issue for experienced sailors as both charts and tools were available that could give fairly decent latitude readings. Without going into detail, the ability to see either the Sun at noon during the day or Polaris (the North Star) at night in general allows a determination of latitude at sea.

Determining longitude can theoretically make use of similar tools as used for latitude (which are various devices, really, just to determine the angle between the horizon and Sun or stars), however, due to the geographical (and for that matter geometric) nature of longitude, accurate determination of longitude also requires another piece of information: time.

Time has a strong relationship to longitude because the Earth rotates at fifteen longitude degrees per hour. Accordingly, if a sailor knew the time at a fixed reference location and then knew the local time, they could, through the wonders of math (or at least the wonders of a chart) figure out their longitude.

Finding out the local time wasn’t typically a major problem at the time, but the fly in the ointment in the aforementioned system is knowing the time, accurately, at the used fixed reference location. Note this isn’t just a matter of having a chronometer, but one that’s extremely accurate, as a single degree of longitude could be a fairly decent distance in terms of kilometers (the actual distance varied relative to the distance to the poles).

Prior attempts to solve the longitude problem involved some very bright minds, including Galileo and Edmond Halley, examining the issue with a particular focus on celestial bodies. Improved sextants and the development of a method using the moon, the so-called lunar distance method had some utility in the mid-18th century, but at the beginning of the 18th century, the longitude problem remained a critical issue, and even the later lunar distance method still had some accuracy issues.

One of the main practical methods of longitude calculation actually used at the time was dead reckoning, which involved making estimates based off course and speed in relation to a known starting point. This method is subject to severe cumulative error, and that is assuming that the navigators are keeping good records.

In addition, a lack of accurate knowledge of longitude could cause navigators to lean more on their knowledge of latitude. For example, they might establish travel until they were at the known latitude of their destination and then just sail directly toward it by maintaining latitude. This might, in many circumstances, mean they were not traveling the most direct route.

Now, one might ask, “What’s the big deal? So they didn’t have the most accurate navigation in the world. They got around, right? Heck, they got across the ocean to the New World.”

First of all, for those not traveling the most direct route, this meant more time on the ship. If they were in the middle of the ocean, this meant issues with supplies.

Second, incorrect navigation away from the coast could be downright dangerous. This was spectacularly demonstrated in 1707 when a fleet commanded by Sir Cloudesley Shovell attempted to return from a failed naval campaign in Gibraltar.

From September to October, the fleet traveled without serious incident. Bad weather had slowly put them off course. This all came to head on October 22. The fleet, at the time, thought they were much farther west than they actually were, and, as a consequence, were not aware they were sailing right into the Isles of Scilly off the Cornish Peninsula.

By the time they realized their mistake, it was too late. The fleet struck ground. Four ships were lost and at least 1400 sailors died.

While this was not the only such disaster, it was a particularly high-profile one. Something had to be done to save the lives of English sailors. In 1714, the Longitude Act was passed, and the Board of Longitude was established. The Board offered prizes for men who could solve the longitude problem.

There were three main longitude prizes: 10,000 pounds for a method that could accurately determine longitude within sixty nautical miles, 15,000 pounds for a method for within forty nautical miles, and 20,000 pounds for a determination within thirty nautical miles.

Although it is difficult to completely accurately determine the relative inflation between 1714 and now, that still puts the rough value of the prizes in the neighborhood of tens of millions of modern pounds. So, in other words, the Board of Longitude was throwing around just as much money, in equivalent terms, as the Ansari X Prize.

Although many brilliant men tackled the problem, an autodidact carpenter and clockmaker is the man who ultimately solved the issue in a lasting and accurate way. He spent decades of his life attempting to construct accurate clocks that would allow for accurate time-keeping on the ship and keep track of the time from the reference point. Ultimately, he designed a series of large watch maritime chronometers for the purpose.

Despite the accuracy of Harrison’s later devices, the Board of Longitude claimed, basically, that he’d gotten lucky. Now, there are many possible reasons for that, but two major reasons commonly cited by historians include the presence of a professional rival on the Board of Longitude at the time of certain critical tests and an academic preference for non-chronometer-based methods, as certain alternate methods, such as the lunar distance method, were viewed by the scientific establishment as being more reflective of science. There’s also some suggestion that the Board may have been biased against Harrison because of his relatively humble background.

Eventually, nearing the end of his life and finding the Board intransigent, Harrison managed to appeal to King George III, who tested Harrison’s most advanced watch himself in 1772 (though at the palace, not on a ship). With the king vouching for the accuracy of his devices, Parliament begrudgingly was forced to award some money to Harrison, though he was never officially awarded the Longitude Prize, even though he obtained about the same amount of money overall through various payments from Parliament. He didn’t have long to enjoy it, as he died in 1776, though his family at least benefited.

As they never officially granted the prize, the Board of Longitude had no reason to close up shop, but they would officially be disbanded by Parliament in 1828.

I should briefly note that other countries also established similar sorts of longitude prizes and navigation awards. This was one of the foremost scientific and maritime issues of the 17th and 18th centuries.

As mentioned above, the lunar distance method had gained some popularity in the middle of the 18th-century and traction over marine chronometers because it was cheaper, but ultimately Harrison’s chronometers (and later marine chronometers) were more accurate, and so in the 19th century, chronometers came to dominate.

Even modern GPS is, ultimately, a time-based technology, as demonstrated, interestingly enough, in the James Bond movie Tomorrow Never Dies, where a disruption in a satellite chronometer is used by a villain to disastrous navigational effect against a Royal Navy frigate. So, Harrison definitely got the last laugh in the long run as no supervillains have made use of the lunar distance method for their plots yet.

~~~~~~~~~~~~J.A. Beard is a scientific editor and the author of A Woman of Proper Accomplishments, which is a Regency paranormal romance about a bunch of landlubbers from Bedfordshire, so no longitude calculations are involved.

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